Oxide interfaces: Watch out for the lack of oxygen

Interfaces between certain insulating perovskite oxides, where oxygen vacancies is important, show unusual properties such as high conductivity and magnetism. Ohtomo and Hwang have reported the development of a strong conducting two-dimensional electron-transport channel at the interface between the two perovskite oxides, LaAlO₃ (LAO) and SrTiO₃ (STO). Each of the two compounds is a strong electric insulator, however, when combined in a heterostructure, unusually generate a conducive channel with transport properties superior to more conventional two-dimensional electron gases. The chemical potential for electrons in the surface layer increases as the crystal grows due to the unidirectional electric field. This unusual property found in oxide system heterostructures may lead to useful devices with novel characteristics.